In recent years, considerable effort has been spent in developing low cost optical packages. Optical communication technology has increased in popularity in the data communications and telecommunications industries over the past several years. The packaging is a high cost element of producing optical devices because of the difficulties surrounding alignment and connection of optical devices and optical fibers. Alignment of laser diodes and optical fibers is a slow, labor intensive task and automation of this process is extremely difficult. As a result, the cost of using most optical packages is high.
Recently, silicon optical benches have been developed to reduce the cost involved with packaging optical circuits. A silicon optical bench is a silicon platform on which a number of optical devices can be packaged. The optical devices are manufactured in a semiconductor chip, and the chip is mounted to the silicon optical bench. Using a silicon optical bench allows several optical circuits on a plurality of chips to be packaged on a single platform or bench.
To mount a chip containing an optical circuit on a silicon optical bench requires contact to be made between the contacting areas on the chip and the bench itself. One side of an optical device chip normally comprises a P contact or an N contact surface, while the opposite side comprises a complimentary contact. The bottom side of the chip is soldered directly to the silicon optical bench to provide contact between the bench and one contacting layer. The chip is first placed on solder pads located on the optical bench, and then the solder is re-flowed to affix the chip to the bench. Contact is made to the complimentary contact layer using one or more bond wires.
FIG. 1 illustrates an optical device chip 50 mounted to a silicon optical bench 52 in accordance with the prior art. Referring to FIG. 1, contact is made between the P contact pad 54 and the silicon optical bench 52 using a solder pad 53. Contact is made to the N contact area 56 on the top of the chip using a bond wire 58 between the N contact area 56 on the top of the chip and an additional contact region located on the silicon optical bench (not shown).
Despite the advantages of using a silicon optical bench, the mounting of optical chips remains a high cost, labor intensive process. The optical chip must be actively aligned with the desired location on the silicon optical bench during the installation process. In addition, once the chip has been soldered to the silicon optical bench, the bond wires must be individually installed to make contact to the top surface of the chip. This makes automation difficult and requires expensive, high precision equipment.
In addition to manufacturing concerns, the bond wires also introduce additional parasitic parameters (e.g., capacitance, inductance) into the circuit. The bond wires also cause a higher failure rate of the circuit by providing an additional component subject to failure or defect.
Non-optical device chips have been developed that have both the P contact and the N contact residing on the same side of the device. These chips are known in the art as “flip chips.” However, the fabrication of conventional flip chips requires via holes to be etched through the chip to create a contact from the top side of the chip to the bottom side of the chip. The creation of these vias add additional processing steps, which has made fabrication of optical devices in a flip chip configuration unpractical.
Accordingly, there is a need for an optical chip that can be quickly and easily mounted to a silicon optical bench without requiring bond wires or extensive alignment. The present invention fulfills this need among others.